1. Technical Field of the Invention
The present invention relates to the field of electronics, and more particularly to device and method to detect parked vehicles at night.
2. Prior Arts
Locating a vacant parking space causes much frustration to motorists. It increases fuel consumption and has a negative impact to the environment. To conserve energy resources and enhance the quality of the environment, it is highly desired to develop a parking-monitoring system, which can transmit substantially real-time parking states (i.e. occupied or vacant) to motorists. Based on the parking states, a motorist can be guided towards a vacant parking space at destination.
Parking enforcement is an important aspect of city management. The current parking-enforcement system is patrol-based, i.e. parking enforcement officers patrol the streets and/or parking lots to enforce the parking regulations. This operation requires significant amount of man power and also consumes a lot of fuel. It is highly desired to take advantage of the above-mentioned parking-monitoring system and automatically measure the parking time for each monitored parking space.
Both parking monitoring and enforcement are based on parked vehicle detection. To detect a parked vehicle, prior arts use a camera to capture the image of a parking area, from which to extract the parking state. Relying on the natural lighting to capture images, prior arts only work during the day. At night, the camera cannot capture the image of the parking area under low ambient lighting. As a result, the parking state cannot be extracted.
U.S. Pat. No. 7,652,593 B1 issued to Haynes et al. on Jan. 26, 2010 discloses a parking management system. It comprises a plurality of video input devices 1420 and parking lot lights 1225. The parking lot lights 1225 can be used to illuminate the parking lot at night. However, to monitor a large number of street parking spaces, a large number of street lights need to be installed, which would be expensive. Haynes also discloses various types of vehicle indicators (e.g. position indicator, engine indicator and direction indicator), whose outputs may be used to extract the parking state. However, most existing vehicles are not equipped with these indicators. Installing them on each vehicle is impractical.